Subseasonal Prediction of European Extreme Temperature ...

Subseasonal Prediction of European Extreme

Temperature Events in S2S hindcasts

Ole Wulff

&

Daniela Domeisen

Institute for Atmospheric and Climate Science

Summer of 2018

ECMWF Ensemble mean 2m temperature anomaly forecast (shading) and ensemble spread

(contours) averaged over Scandinavia

Subseasonal prediction of extreme temperatures in Europe

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Objectives

Is there extended prediction skill for extreme surface temperature

events (compared to climatologically average ones)?

What is the role of persistence?

Subseasonal prediction of extreme temperatures in Europe

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Verification of S2S ensemble hindcasts

Surface temperature variability can be

determined by components with

predictability potential on S2S time

scales:

? low-frequency atmospheric

variability (possibly influenced by

ocean variability, Cassou et al., 2005;

Wulff et al., 2017)

? land-atmosphere interactions (soil

moisture memory, Seneviratne et al.,

2010)

from Cassou et al., 2005

from Seneviratne et al., 2010

Subseasonal prediction of extreme temperatures in Europe

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Data & Methods

Data:

Hindcasts: S2S ensembles (Vitart et al., 2016)

? mostly ECMWF: 11 members, initialized twice weekly, only model versions 2016+

Verification: ERA-Interim reanalysis (Dee et al., 2011)

Methods:

Consider pentad mean anomalies of ??2?? in JJA with respect to the 1999-2010 lead

time-dependent climatology

5??

Extreme temperature event: exceedance of the 95th percentile of the ??2??

distribution

(again lead time-dependent)

Subseasonal prediction of extreme temperatures in Europe

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